#iChannel0 "https://s2.loli.net/2023/09/10/QozT59R6KsYmb3q.jpg"

void mainImage(out vec4 fragColor, in vec2 fragCoord) {

    vec2 uv=fragCoord/iResolution.xy;
    vec3 tex=texture(iChannel0,uv).xyz;

    vec3 col = tex;

    vec2 p = uv;
    p -= .5;
    float d = length(p);
    //col = vec3(d);
    float c = smoothstep(.8,.4, d);
    col *= c;

    fragColor = vec4(col, 1.);
}